Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Evaluation of Electrical Stunning of Atlantic Cod (Gadus morhua) and Turbot (Psetta maxima) in Seawater
    Lambooij, E. ; Digre, H. ; Erikson, U. ; Reimert, H.G.M. ; Burggraaf, D. ; Vis, J.W. van de - \ 2013
    Journal of Aquatic Food Product Technology 22 (2013)4. - ISSN 1049-8850 - p. 371 - 379.
    catfish clarias-gariepinus - fresh-water - slaughter - salmon - consciousness - behavior - quality - l.
    The aim of this study was to assess electrical stunning of Atlantic cod and turbot in seawater to develop a protocol for the process of stunning and killing. An induced general epileptiform insult (unconscious) had a duration of 40 ± 27 s (n =14) in cod (2.6 ± 0.5 kg) and 34 ± 18 s (n = 19) in turbot (520 ± 65 g). Seven cod and 3 turbot displayed a physical reaction, and 11 turbot registered an electroencephalogram (EEG) response to pain stimuli administered 30 s post-stun. The heart rate was 32 ± 6 beats/min in cod and 25 ± 7 beats/min in turbot prior to stunning. Post-stunning, the electrocardiogram (ECG) revealed fibrillation and reduced activity post-stun. EEG, ECG recordings, and behavioral observations indicate that when a bipolar square wave current was applied with a frequency of 133 Hz and 43% duty cycle side to side (turbot) and at 170 Hz and 33% duty cycle (cod) head to tail, both species were stunned in seawater at current densities of 3.2 A/dm2 and 2.5 A/dm2, respectively. For turbot, a 5 s exposure to electricity followed by chilling in ice water for 15 min is sufficient to prevent recovery. For cod, a killing method needs to be established.
    Behavioural indicators of welfare in farmed fish
    Martins, C.I. ; Galhardo, L. ; Noble, C. ; Damsgard, B. ; Spedicato, M.T. ; Zupa, W. ; Beauchaud, M. ; Kulczykowska, E. ; Massabuau, J.C. ; Carter, T. ; Planellas, S.R. ; Kristiansen, T. - \ 2012
    Fish Physiology and Biochemistry 38 (2012)1. - ISSN 0920-1742 - p. 17 - 41.
    trout oncorhynchus-mykiss - salmon salmo-salar - catfish clarias-gariepinus - bass dicentrarchus-labrax - repeat swimming performance - brain serotonergic activity - juvenile atlantic salmon - bream sparus-aurata - divergent stress responsiveness - char salvelinus
    Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e.g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e.g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.
    Assessing effectiveness of electrical stunning and chillingin ice water of farmed yellowtail kingfish, common sole and pike-perch
    Llonch, P. ; Lambooij, E. ; Reimert, H.G.M. ; Vis, J.W. van de - \ 2012
    Aquaculture 364-365 (2012). - ISSN 0044-8486 - p. 143 - 149.
    catfish clarias-gariepinus - atlantic cod - fresh-water - fish - temperature - quality - stress - brain - l.
    Animals should be rendered unconscious before slaughter in order to avoid suffering or pain. The objective of this study was to evaluate an electrical stunning after dewatering to induce instantaneous unconsciousness and insensibility in yellowtail kingfish (Seriola lalandi), common sole (Solea solea) and pike-perch (Stizostedion lucioperca). To kill without recovery, the current was applied for 5 s, followed by chilling in ice water for 10 min. Loss of consciousness and sensibility were assessed by neural (EEG), physiological (ECG) and behavioural parameters. An epileptiform insult was observed in all yellowtail kingfish (n = 27), common sole (n = 25) and pike-perch (n = 25) after administering a current of 0.54 +/- 0.12 A(rms) (124 V dc and 11 V-rms ac; 100 Hz), 0.65 +/- 0.23 A(rms) (98 V dc and 8.4 V-rms ac; 100 Hz) and 0.75 +/- 0.24 A(rms) (144 V dc and 13 V-rms ac; 100 Hz) during 1 s through the head of individual fish, respectively. When yellowtail kingfish (n = 11) was submitted to a 5 s electrical stun followed by chilling in ice water, this resulted in passing 0.72 +/- 0.13 A(rms) for 5 s and no recovery during chilling. In the case of common sole (n = 10) and pike-perch (n = 12), passing 1.4 +/- 0.64 and 0.75 +/- 0.24 A(rms) during 5 s followed by chilling in ice water for 10 min resulted in an irrecoverable stun in 9 out 10 fish and 11 out 12 fish, respectively. We conclude that for yellowtail kingfish the investigated combination of electrical stunning and chilling is suitable for humane slaughter, whereas for common sole and pike-perch this procedure needs to be optimised. (C) 2012 Elsevier B.V. All rights reserved.
    Feeding behavior and stress response explain individual differences in feed efficiency in juveniles of Nile tilapia Oreochromis niloticus
    Martins, C.I. ; Conceição, L.E.C. ; Schrama, J.W. - \ 2011
    Aquaculture 312 (2011)1-4. - ISSN 0044-8486 - p. 192 - 197.
    catfish clarias-gariepinus - salmon salmo-salar - beef-cattle - atlantic salmon - rainbow-trout - growth-performance - genetic-variation - metabolic differences - food-consumption - body-composition
    Feed efficiency is a trait of enormous importance in any animal production sector including aquaculture. Individuals that are more feed efficient need to use less feed to achieve similar growth rates as compared to less efficient individuals. Considering that feed represents the largest cost of production and one of the main causes for the ecological footprint of a farm, more knowledge on the extent of individual differences in feed efficiency and underlying physiological processes are needed. This study is the first to investigate individual differences in feed efficiency, measured as residual feed intake and its relationship with feeding behaviour and stress response in one of the most important farmed fish, the Nile tilapia. The individual feed intake of twenty-four juvenile of Nile tilapia was followed during 57 days. Fish were fed until apparent satiation with a commercial feed twice per day. Individual feed behavior was registered once per week and consisted on measuring the latency to start feeding (LAT, min), total feeding time (TFT, min) and the number of feeding acts (NFA, min). Blood samples for plasma cortisol was taken at the end of the experiment (control, indicative of undisturbed levels) and after a stress test (netting), 15 days after the previous sampling. Individual growth rates and residual feed intake were determined at the end of the experiment. Results show pronounced individual differences in residual feed intake as well as a significant correlation with both feeding behavior (feeding latency, total feeding time and number of feeding acts) and stress (cortisol) response. Cortisol levels obtained after the stress test and feeding behavior could explain differences in residual feed intake by 4%. These results show that individuals with higher feeding activity and higher cortisol response are less efficient fish. This suggests that individual differences in feeding activity and stress response explain part of the differences in feed efficiency by explaining variance in maintenance energy expenditure.
    Percussion and electrical stunning of Atlantic salmon (Salmo salar) after dewatering and subsequent effect on brain and heart activities nd subsequent
    Lambooij, E. ; Grimsboe, E. ; Vis, J.W. van de; Reimert, H.G.M. ; Nortvedt, R. ; Roth, B. - \ 2010
    Aquaculture 300 (2010)1-4. - ISSN 0044-8486 - p. 107 - 112.
    catfish clarias-gariepinus - current duration - field strength - slaughter - injuries - fresh - l.
    The overall objective of the study was to evaluate a percussive and an electrical stunning method under laboratory conditions in Atlantic salmon. Evidence of unconsciousness and insensibility of the salmon was provided on the electroencephalogram (EEG) by the appearance of slow waves and spikes, followed by a strong depression in electrical activity. This phenomenon was observed in 17 salmon after percussive stunning using an air pressure of 8.1 to 10 bars, whilst 8 fish were considered conscious at pressures below 8.1 bars although some were seemingly unconscious on behaviour. Consequences were a haemorrhage in the brain cavity in 15 out of 17 fish, broken upper or lower jaws in 9 fish and eye burst in 8 fish. A general epileptiform insult (unconscious and insensible) was obtained by delivering a voltage, consisting of a direct current (DC) coupled with 100 Hz alternating current (AC) with a peak value of ˜112 volt (V), head to body, for ˜ 0.5 s. The total duration of the insult was 62 ± 44 s (mean ± SD; n = 25) which was followed by minimal brain activity in 19 fish. The heart rate was 20 ± 7 beats/min prior to stunning. After stunning the electrocardiogram (ECG) revealed fibrillation for 22 ± 15 s and became irregular and showed extra systolae (ventrical contraction) afterwards. Exposing the salmon for 5 s with electricity followed by a gill cut resulted that 1 out of 3 fish recovered temporary after 3 min. Haemorrhages were not observed in the fillets. Average current for head to body electrical dry stunning was 668 milliampere (mA) root mean square (RMS) with an average stunning voltage of 107.9 Vrms. Electrical head to body stunning can be recommended when using coupled AC and DC current of 668 mArms and ˜ 107 Vrms. The salmon can be stunned in ˜ 0.5 s. However, a correct bleeding procedure should be developed. For percussive stunning we conclude that if sufficient force is used the fish will be rendered unconscious insensible which result in damage of the carcass, whereas a combined AC and DC can be recommended source for dry electrical head to body stunning.
    Is growth retardation present in Nile tilapia Oreochromis niloticus cultured in low water exchange recirculating aquaculture systems?
    Martins, C.I. ; Ochola, D. ; Ende, S.S.W. ; Eding, E.H. ; Verreth, J.A.J. - \ 2009
    Aquaculture 298 (2009)1-2. - ISSN 0044-8486 - p. 43 - 50.
    catfish clarias-gariepinus - stress-response - stocking density - fish - l. - efficiency - ph
    It has been suggested that fish cultured in recirculating aquaculture systems (RAS) grow less as compared with fish cultured in flow-through systems due to the accumulation of substances. In the Netherlands, the commercial culture of Nile tilapia Oreochromis niloticus in 300 and 600 MT's systems is done exclusively in RAS operated at water exchange ratesas low as 30 L/kg feed/day due to nitrate control by single-sludge denitrification reactors. The use of such nearly closed RAS raises the question whether growth retardation (GR) is present in Nile tilapia. This study is the first to investigate the existence of growth retardation in Nile tilapia by comparing the growth, feeding behaviour and stress response of Nile tilapia cultured in RAS with different levels of substances accumulated. Three RAS, operated at 30 L/kg feed/day (HIGH accumulation), 70 L/kg feed/day (MIDDLE accumulation) and 1500 L/kg feed/day (LOW accumulation) were used. Each RAS contained 24 glass aquaria with individually housed fish. To determine whether GR is size-dependent, per RAS 3 fish size categories were tested in the 57 day experimental period: large (288.7 +/- 34.2g; N=8), medium (162.4 +/- 23.4g: N=8) and small (81.4 +/- 21.0g; N=8). Experimental fish were fed ad libitum, twice per day. Feeding behaviour was determined once per week and was measured as the time taken by each fish to eat the first pellet (latency, LAT) and the total time spent feeding (total feeding time, TFT). Temperature, pH. conductivity, alkalinity, dissolved oxygen, dissolved CO2, nitrogen compounds (TAN, NO2-N and NO3-N), chemical oxygen demand and orthophosphate-P were measured over time. At day 57 fish were weighed, blood sampled and returned to their tanks for an extra experimental period of 15 days, and subjected at day 72 to an acute stress followed by blood sampling. Blood was analysed for glucose and cortisol. Results showed that the water quality parameters measured in the 3 RAS (with the exception of alkalinity) were still within the optimum range for growth of Nile tilapia. Large individuals showed a tendency to grow more in the LOW treatment (2.66 +/- 1.35 g/kg(0.8)/day) as compared with the MIDDLE treatment (0.93 +/- 1.63 g/kg(0.8)/day). On the contrary, small individuals grew significantly less in the LOW treatment (3.60 +/- 1.74 g/kg(0.8)/day) as compared with the HIGH (7.22 +/- 1.58 g/kg(0.8)/day) and MIDDLE (6.82 +/- 4.54 g/kg(0.8)/day) treatments. Small fish were more motivated to eat (lower latency) in the MIDDLE (4.63 +/- 5.24 min) as compared with the LOW treatment (8.94 +/- 6.41 min). In the HIGH accumulation treatment higher glucose levels were observed in the small fish, before and after acute stress, as compared with the LOW accumulation treatment. In conclusion, this study showed that the extent to which the accumulation of substances in RAS affects growth depends on fish size: large individuals show a trend towards growth retardation in the highest accumulation RAS while small individuals, on the contrary, seem to grow better in such systems.
    A humane protocol for electro-stunning and killing of Nile tilapia in fresh water
    Lambooij, E. ; Gerritzen, M.A. ; Reimert, H.G.M. ; Burggraaf, D. ; Vis, J.W. van de - \ 2008
    Aquaculture 275 (2008)1-4. - ISSN 0044-8486 - p. 88 - 95.
    catfish clarias-gariepinus - anguilla-anguilla l. - fish - consciousness - slaughter - quality - pain
    Behavioural, neural and physiological parameters were scored after electro-stunning of Nile tilapia (Oreochromis niloticus) in three positions to an electric field in fresh water. An overall current density, 1.0 Arms/dm2, 50 Hz sinusoidal, applied for 1 s top-to-bottom in water (700 ¿S/cm), induced a general epileptiform insult on the EEG for 26 ± 10 s (n = 24). The ECG revealed fibrillation for 9 ± 4 s in 15 out of 24 fish. To kill without recovery, the current was applied for 5 s, followed by chilling in ice water for 15 min. Killing of the stunned fish by gill-cutting instead of chilling is not recommended, as 2 out 4 tilapias responded 10 min post stun. When electricity was applied head-to-tail on tilapia (n = 8), the overall current density could be reduced to 0.4 Arms/dm2, 50 Hz sinusoidal, to induce a general epileptiform insult, which lasted 27 ± 10 s. A pulsed square wave alternating current (overall density of 0.6 Arms/dm2, 133 Hz and 43% duty cycle) was applied for 1 s side-to-side on tilapia in water (650 ¿S/cm). This induced a general epileptiform insult for 51 ± 37 s (n = 14). Fibrillation occurred for 16 ± 7 s (n = 10). Free-swimming fish righted between 68 and 95 s (n = 5) and between 438 and 1139 s (n = 5) after 1 and 5 s electro-stunning, respectively. Our results show that protection of welfare of tilapia at slaughter can be obtained with electro-stunning followed by killing the stunned fish in ice water.
    Evaluation of electrical stunning of sea bass (Dicentrarchus labrax) in seawater and killing by chilling: wel;fare aspects, product quality and possibilities for implementation
    Lambooij, E. ; Gerritzen, M.A. ; Reimert, H.G.M. ; Burggraaf, D. ; Andre, G. ; Vis, J.W. van de - \ 2008
    Aquaculture Research 39 (2008)1. - ISSN 1355-557X - p. 50 - 58.
    catfish clarias-gariepinus - anguilla-anguilla l. - salmon salmo-salar - atlantic salmon - slaughter method - rigor-mortis - consciousness - frequency - texture - fresh
    The objective was to assess neural, behavioural responses and product quality in farmed sea bass (Dicentrarchus labrax) upon electrical stunning in seawater. The electrical sinusoidal 50 Hz or pulse square wave alternating 133 Hz current induced a general epileptiform insult with a current of 3.3±0.2 or 3 A dm¿2, respectively, for 1 s head to tail in seawater. The total duration of the insult was 48±34 and 23±11 s. After stunning, the electro-cardiogram revealed fibrillation and ceased or showed malfunction. Product quality was assessed in a group electrically stunned, followed by chilling in ice water and the controls were only chilled in ice water. The pH of the fillets was 0.1¿0.2 lower (P
    Electrical and percussive stunning of the common carp (Cyprinus carpio L.): Neurological and behavioural assessment
    Lambooij, E. ; Pilarczyk, M. ; Bialowas, H. ; Boogaart, J.G.M. van den; Vis, J.W. van de - \ 2007
    Aquacultural Engineering 37 (2007)2. - ISSN 0144-8609 - p. 171 - 179.
    catfish clarias-gariepinus - anguilla-anguilla l. - welfare aspects - fish - pain - slaughter - awareness - calves
    The overall objective of the study was to evaluate electrical and percussive stunning methods under laboratory conditions in common carps. The electrical current needed to induce a general epileptiform insult was assessed in 13 carps. The insult was obtained by delivering a current of 0.24 ± 0.03 A (163 ± 1 V; 50 Hz, a.c.) to the head, via scissor-model stunning tongs for approximately 1 s. The duration of the tonic, the clonic and the exhaustion phases were 11 ± 4 s, 5 ± 3 s and 20 ± 14 s on the EEG, respectively. An actual clonic phase was observed in two fish. The total duration of the insult was 31 ± 14 s. The heart rate was 22 ± 12 beats/min prior to stunning while after stunning, the ECG revealed fibrillation for 18 ± 7 s and was irregular. The behaviour of 10 individual carp, which were allowed to move freely in water, was recorded following head-only stunning (164 V, 0.23 ± 0.6 A). The duration of the tonic phase was approximately 10 s and the fish started fin movements after 48 ± 8 s and resumed swimming after 121 ± 83 s. A general epileptiform insult could be induced in carps (n = 25) by passing an electrical current through fresh water using 0.14 ± 0.03 A/dm2 (113 ± 17 V; electrode distance 16 cm) for 1 s at a water conductivity of 200 ¿S/cm. Twenty three carps were rendered unconscious and insensible during electrical stunning in fresh water, using 0.73 ± 0.05 A/dm2 (411 ± 2 V; electrode distance 16 cm) for 5 s at a water conductivity of 330 ¿S/cm, followed by chilling in ice water. As a second stunning procedure, carps were stunned mechanically using a percussion pistol at a maximal velocity of 10.99 ± 0.88 J. Evidence of unconsciousness and insensibility of the carps was provided by the appearance of theta, delta waves and spikes on the EEG, which were proceeded by no brain activity. However, two carp responded after 0.5 min to administered pain stimuli and one carp after 3 min. It may be concluded from this study that common carp are effectively stunned in fresh water. The application of an electrical current of 0.73 A/dm2 (26 V/cm, 50 Hz, a.c., 330 ¿S/cm) to individual carps in a tank in combination with chilling in ice water is an effective procedure for slaughter. The mechanical method of percussion stunning did not provide assurance of effective stunning as not all carp were unconscious and insensible after its administration.
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